Real-time audio, such as a telephone conversation between two people using telephones, may be transmitted over a packet network such as the Internet using Voice over Internet Protocol (“VoIP”). VoIP may be used instead of transmitting the telephone conversation over a Public Switched Telephone Network (PSTN) connection in order to take advantage of expanded service offerings and/or to eliminate or reduce charges for a long distance telephone call.
To transmit the real-time audio over the packet network, a packet transmitter in a source Internet node encodes the analog voice signal, loads the encoded data in the payload of one or more data packets, and transmits the data packets over the packet network.
In a system in which real-time audio can be directed over a packet network or a telephone network, a caller can select the method of transmission. The caller may want to select the method of transmission based on cost, features, or quality of the call. VoIP calls typically offer lower cost; although this may not be the case, for example, if the caller has an unlimited calling plan on a PSTN connection. A VoIP service typically offers more premium features than a PSTN service, such as real-time availability of call logging information. Call quality may suffer from time to time on a VoIP connection, such as when there is high Internet traffic. Conversely, in many situations VoIP call quality is superior to that available through a PSTN connection. This is often the case for international calls, where the cost advantages for VoIP are typically greatest.